1. Field
One embodiment of the invention relates to an information storage apparatus, a servo pattern formation control apparatus, and a recording medium.
2. Description of the Related Art
In information storage apparatuses such as magnetic disk apparatuses, servo patterns that are used for positioning control of a record reproducing head are formed on a recording medium, such as a magnetic disk. An information storage apparatus uses the servo patterns read by the record reproducing head to position the record reproducing head in a target data track on a recording medium.
In general, the servo patterns that are formed on the recording medium are formed radially from the inside of the recording medium to the outside thereof. As another shape of the servo patterns, the servo patterns may be formed in a spiral shape and a concentric circle shape connected to the spiral shape (for example, see Japanese Patent Application Publication (KOKAI) No. S61-59671).
The servo patterns are formed on the recording medium using a process called servo track writing (STW). For example, a method that magnetically records the servo patterns on the entire surface of the recording medium by external STW equipment needs a large amount of time during a write operation, and needs the external STW equipment for a long time. Accordingly, an equipment investment cost of the external STW equipment may be increased.
In order to decrease the equipment investment cost of the external STW equipment, a method that magnetically writes servo patterns by a record reproducing head of an information storage apparatus has been suggested (for example, see U.S. Pat. No. 5,668,679 and U.S. Pat. No. 7,145,744). According to the method, a spiral servo pattern is formed by the record reproducing head of the information storage apparatus, and a radial servo pattern is formed using the spiral servo pattern.
In the method that forms the servo patterns using the spiral servo pattern as a reference, since the spiral servo pattern does not have absolute position information on the recording medium, an absolute position on the recording medium cannot be specified directly from the spiral servo pattern. Hence, it is difficult to specify a write start position of the servo patterns.